The polyol 1,3-propanediol (PDO) is a monomer useful in the production of a variety of polymers including polyesters, polyurethanes, polyethers and cyclic compounds. The polymers are ultimately used in fibers, films, coatings, composite materials, solvents, anti-freeze, copolyesters and other value-added applications.
1,3-propanediol may be produced synthetically or by fermentation. A variety of chemical routes to generate 1,3-propanediol are known. For example, 1,3-propanediol may be generated from 1) ethylene oxide over a catalyst in the presence of phosphine, water, carbon monoxide, hydrogen, and an acid; 2) by the catalytic solution phase hydration of acrolein followed by reduction; or 3) from hydrocarbons (such as glycerol) reacted in the presence of carbon monoxide and hydrogen over catalysts having atoms from Group VIII of the Periodic Table.
1,3-propanediol produced biologically via fermentation is known, including in U.S. Pat. No. 5,686,276, U.S. Pat. No. 6,358,716, and U.S. Pat. No. 6,136,576, which disclose a process using a recombinantly-engineered bacteria that is able to synthesize 1,3-propanediol during fermentation using inexpensive carbon sources such as glucose or other sugars.
Both the synthetic and fermentative routes to producing 1,3-propanediol generate residual materials that can compromise the quality of the polymers produced from this monomer. Particularly, 1,3-propanediol produced via fermentation contains residual organic impurities that contribute to color and odor aspects in the polyol, and ultimately in the polymers made therefrom.
Fisher et al. disclose in WO 00/24918 a method for purifying a polyol product from a culture generated by a polyol-producing microorganism. The method employs a pretreatment operation that includes microbial cell separation without killing or disrupting the microbes, in combination with removal or deactivation of proteinaceous material. Subsequent purification steps include further removal or deactivation of proteinaceous materials using methods such as froth flotation or flocculation, followed by absorption/adsorption, with further treatments including ion exchange chromatography, activated carbon treatment, evaporative concentration, precipitation and crystallization. The primary goal of the Fisher methodology is to remove proteinaceous contaminants to below a negligible level so that the purified polyol will be suitable for use in food grade products.
George et al. disclose in U.S. Pat. No. 5,034,134 a method for separating impurities from ethylene glycol product streams, particularly aliphatic organic acids, by contacting the ethylene glycol product stream with suitable semi-permeable membranes. A primary goal of the method is to remove UV absorbing molecules and UV absorbing precursors so as to make the purified ethyl glycol monomers suitable for the manufacture of polyesters.
A process for reclaiming lower glycols such as monoethylene glycol, 1,2-propylene glycol and 1,3-propanediol from operative fluids such as antifreeze solutions, heat transfer fluids, deicers, lubricants, hydraulic fluids, quenchants, solvents and absorbents, by contacting the fluid with semi-permeable membranes under reverse osmosis is disclosed in George et al., U.S. Pat. No. 5,194,159.
Haas et al., U.S. Pat. No. 5,334,778, disclose a process for the production for 1,3-propanediol produced from 3-hydroxypropionaldehyde in the presence of a fixed bed or suspension hydrogenation catalyst, wherein the residual carbonyl content of the purified 1,3-propanediol is disclosed to be below 500 ppm.
A process for the treatment of aqueous solutions of polyhydric alcohols to remove heavy metal components, oils and organic contaminants is disclosed in U.S. Pat. No. 5,510,036, Woyciesjes et al., wherein the process comprises a series of pH adjustments of the aqueous solution and additions of various precipitating, flocculating or coagulating agents. Precipitated contaminants are removed from the aqueous solution using filtration means, optionally followed by an ion exchange step.
Haas et al., U.S. Pat. No. 6,232,512 B1, is directed to a method for reducing the content of acetals or ketals in alcohol-containing reaction mixtures. The method comprises hydrogenation of the reaction mixture containing cyclic acetal or ketal with a 1,3-dioxo structure using a Pd and/or Ru activated carbon catalyst, on a trickle-bed reactor at a pH of about 6.5 to 7.0.
A process for preparing 1,3-propanediol-based polyester is disclosed in Kelsey et al., U.S. Pat. No. 6,245,879 B1. The process entails first polymerizing terephthalic acid and a molar excess of 1,3-propanediol to produce polytrimethylene terephthalate, wherein the excess 1,3-propanediol is recovered from the distillate of the reaction by pH adjustment and further distillation. The recovered 1,3-propanediol is then recycled to the original polymerization reaction stream for further reaction with terephthalic acid. Optionally, the reaction stream can be further treated with a borohydride.
Anderson et al., WO 01/25467A1 disclose a fermentation medium containing an energy source, a source of inorganic nitrogen, phosphate and biotin, and at least one metal selected from an alkali metal, an alkaline earth metal and transition metals. The disclosed medium is stated to be conducive to supporting the synthesis of polycarboxylic acids, polyols and polyhydroxy acids via fermentation methods.
U.S. Pat. No. 4,380,678, to Sirkar, A. K., discloses a multi-staged process for conversion of aldoses to polyols. The process first catalytically hydrogenates the aldose in a fixed bed reaction using high activity nickel catalysts, while adjusting the pH to alkaline conditions. The resulting alditols are then catalytically hydrocracked in a second stage fixed bed reaction. Reaction products are recovered in a separation step, and unconverted heavy alditol can be recycled to the second stage fixed bed zone for further hydrogenolysis.
A need exists in the art for a means to efficiently and economically obtain highly purified biologically-produced 1,3-propanediol from fermentation broth, in order that monomers of sufficient purity may produce useful, high-quality polymers that can be obtained by such biological methods. A further need exists in the art to obtain highly purified compositions of 1,3-propanediol derived from any source, including biological or chemical sources, for certain end uses of the diol including polymerization into polymers used for fabrics, and other applications.